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LT3957EUHE#PBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P28
LT3957
1
3957f
n
Wide Input Voltage Range: 3V to 40V
n
Single Feedback Pin for Positive or Negative
Output Voltage
n
Internal 5A/40V Power Switch
n
Current Mode Control Provides Excellent Transient
Response
n
Programmable Operating Frequency (100kHz to
1MHz) with One External Resistor
n
Synchronizable to an External Clock
n
Low Shutdown Current < 1µA
n
Internal 5.2V Low Dropout Voltage Regulator
n
Programmable Input Undervoltage Lockout with
Hysteresis
n
Programmable Soft-Start
n
Thermally Enhanced QFN (5mm × 6mm) Package
TYPICAL APPLICATION
DESCRIPTION
Boost, Flyback, SEPIC and
Inverting Converter
with 5A, 40V Switch
The LT
®
3957 is a wide input range, current mode DC/DC
converter which is capable of generating either positive
or negative output voltages. It can be confi gured as either
a boost, fl yback, SEPIC or inverting converter. It features
an internal low side N-channel power MOSFET rated for
40V at 5A and driven from an internal regulated 5.2V
supply. The fi xed frequency, current-mode architecture
results in stable operation over a wide range of supply
and output voltages.
The operating frequency of LT3957 can be set with an
external resistor over a 100kHz to 1MHz range, and can
be synchronized to an external clock using the SYNC pin.
A minimum operating supply voltage of 3V, and a low
shutdown quiescent current of less than 1µA, make the
LT3957 ideally suited for battery-powered systems.
The LT3957 features soft-start and frequency foldback
functions to limit inductor current during start-up.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
No R
SENSE
and ThinSOT are trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Patents pending.
High Effi ciency Output Boost Converter
FEATURES
APPLICATIONS
n
Automotive
n
Telecom
n
Industrial
Effi ciency vs Output Current
SENSE2
SENSE1
LT3957
10µH
V
IN
SW
GND
FBX
RT SS
INTV
CC
EN/UVLO
SYNC
SGND
95.3k
VC
3957 TA01a
200k
41.2k
300kHz
4.7µF
0.33µF
6.8k
22nF
226k
15.8k
10µF
s2
V
OUT
24V
600mA
V
IN
4.5V TO 16V
10µF
OUTPUT CURRENT (mA)
0
70
EFFICIENCY (%)
75
80
85
90
95
100
100 200 300
400 500
3957 TA01b
600
V
IN
= 12V
LT3957
2
3957f
PIN CONFIGURATION
ABSOLUTE MAXIMUM RATINGS
V
IN
, EN/UVLO (Note 5), SW ......................................40V
INTV
CC
......................................................V
IN
+ 0.3V, 8V
SYNC ..........................................................................8V
VC, SS .........................................................................3V
RT
...............................................................................................
1.5V
SENSE1, SGND ..................Internally Connected to GND
SENSE2 ..................................................................±0.3V
FBX ................................................................. –6V to 6V
Operating Junction Temperature Range
(Note 2) .................................................. –40°C to 125°C
Maximum Junction Temperature .......................... 125°C
Storage Temperature Range .................. –65°C to 125°C
(Note 1)
12 13 14
TOP VIEW
SGND
37
SW
38
UHE PACKAGE
36-LEAD (5mm s 6mm) PLASTIC QFN
15 16 17
36 35 34 33 32 31 30
21
23
24
25
27
28
8
6
4
3
2
1NC
NC
SENSE2
SGND
SENSE1
SW
SW
NC
INTV
CC
V
IN
EN/UVLO
SGND
SGND
SW
SW
NC
NC
SYNC
RT
SS
FBX
VC
GND
GND
GND
GND
GND
GND
20
9
10
T
JMAX
= 125°C, θ
JA
= 42°C/W, θ
JC
= 3°C/W
EXPOSED PAD (PIN 37) IS SGND, MUST BE SOLDERED TO SGND PLANE
EXPOSED PAD (PIN 38) IS SW, MUST BE SOLDERED TO SW PLANE
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3957EUHE#PBF LT3957EUHE#TRPBF 3957
36-Lead (5mm × 6mm) Plastic QFN
–40°C to 125°C
LT3957IUHE#PBF LT3957IUHE#TRPBF 3957
36-Lead (5mm × 6mm) Plastic QFN
–40°C to 125°C
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifi cations, go to:
http://www.linear.com/tapeandreel/
LT3957
3
3957f
ELECTRICAL CHARACTERISTICS
The l denotes the specifi cations which apply over the full operating temp-
erature range, otherwise specifi cations are at T
A
≈ T
J
= 25°C. V
IN
= 24V, EN/UVLO = 24V, SENSE2 = 0V, unless otherwise noted.
PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN
Operating Range 340V
V
IN
Shutdown I
Q
EN/UVLO = 0V
EN/UVLO = 1.15V
0.1 1
6
µA
µA
V
IN
Operating I
Q
VC = 0.3V, R
T
= 41.2k 1.7 2.3 mA
V
IN
Operating I
Q
with Internal LDO Disabled VC = 0.3V, R
T
= 41.2k, INTV
CC
= 5.5V 350 400 µA
SW Pin Current Limit
l
5 5.9 6.8 A
SW Pin On Voltage I
SW
= 3A 100 mV
SENSE2 Input Bias Current Current Out of Pin –65 µA
Error Amplifi er
FBX Regulation Voltage (V
FBX(REG)
) FBX > 0V (Note 3)
FBX < 0V (Note 3)
l
l
1.569
–0.816
1.6
–0.800
1.631
–0.784
V
V
FBX Overvoltage Lockout FBX > 0V (Note 4)
FBX < 0V (Note 4)
6
7
8
11
10
14
%
%
FBX Pin Input Current FBX = 1.6V (Note 3)
FBX = –0.8V (Note 3) –10
70 100
10
nA
nA
Transconductance g
m
(ΔI
VC
/ΔFBX)
(Note 3) 230 µS
VC Output Impedance (Note 3) 5 M
V
FBX
Line Regulation (ΔV
FBX
/[ΔV
IN
• V
FBX(REG)
])
FBX > 0V, 3V < V
IN
< 40V (Notes 3, 6)
FBX < 0V, 3V < V
IN
< 40V (Notes 3, 6)
0.04
0.03
0.06
0.06
%/V
%/V
VC Current Mode Gain (ΔV
VC
/ΔV
SENSE
)
10 V/V
VC Source Current VC = 1.5V, FBX = 0V, Current Out of Pin –15 µA
VC Sink Current FBX = 1.7V
FBX = –0.85V
12
11
µA
µA
Oscillator
Switching Frequency R
T
= 140k to SGND, FBX = 1.6V, V
C
= 1.5V
R
T
= 41.2k to SGND, FBX = 1.6V, V
C
= 1.5V
R
T
= 10.5k to SGND, FBX = 1.6V, V
C
= 1.5V
80
270
850
100
300
1000
120
330
1200
kHz
kHz
kHz
RT Voltage FBX = 1.6V 1.2 V
SW Minimum Off-Time 220 275 ns
SW Minimum On-Time 240 320 ns
SYNC Input Low 0.4
SYNC Input High 1.5
SS Pull-Up Current SS = 0V, Current Out of Pin –10 µA
Low Dropout Regulator
INTV
CC
Regulation Voltage
l
5 5.2 5.45 V
INTV
CC
Undervoltage Lockout Threshold Falling INTV
CC
UVLO Hysteresis
2.6 2.7
0.15
2.85 V
V
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LT3957EUHE#PBF

Mfr. #:
Buy LT3957EUHE#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators High Input Voltage, Boost, flyback, SEPIC and Inverting Converter
Lifecycle:
New from this manufacturer.
Delivery:
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